The human eye functions in such a manner as to perceive the visual impression of a lacquer coated surface as a whole. DE-C-196 05 520 describes a method for determining the visual effect of lacquer coatings. This method involves applying one or more lacquer layers onto the surface of a plane substrate and drying or curing it/them, wherein one of the lacquer layers is applied with a layer thickness gradient, and, on the lacquer coated surface obtained in this manner, one or more surface properties influencing the visual impression is/are then measured by means of one or ore optical measurement methods at measurement points distributed over the entire area in the form of a grid screen, and the particular thickness of the wedge-shaped lacquer layer is also measured. Substrates having a plane surface which are used here are preferably test plates or sheets. These preferably consist of metal. Application of the method known from DE-C-196 05 520 to lacquer coated plastic surfaces is limited by the nature of plastic substrates. Elaborate and complex measurement methods must be used to determine the thickness of lacquer layers on plastic substrates non-destructively, for example the thermal wave method, which may only be performed after calibration on a lacquer layer of the same type and of a known thickness, or the light section method, which is restricted to use on clear lacquer layers.